In multichannel audio reproduction, the positions of the speakers on the reproducing side preferably correspond to the positions of the sound sources. In reality, however, the positions of the speakers on the reproducing side often differ from the positions of the sound sources.
Where the positions of the speakers on the reproducing side differ from the positions of the sound sources, there is occurrence of a sound source that is not located in the speaker's position, therefore how to reproduce the sound of such sound sources is a critical issue.
A technique called VBAP (Vector Base Amplitude Panning) has been suggested as a method of reproducing the sound of a sound source located in a desired position through a speaker located in a desired position (see Non-Patent Document 1, for example).
By VBAP, a target normal position of a sound image is expressed by a linear sum of vectors extending toward two or three speakers located around the normal position. The coefficients by which the respective vectors are multiplied in the linear sum are used as the gains of the audio signals to be output from the respective speakers, and gain adjustment is performed so that a sound image is fixed in the target position.